Sudden Torques in Rover

[Corona688]

So, I'd driven 75km in this rover with no problems, then parked it on this cliff, had lunch, and loaded.

When it loaded, it leaped 50m into the air - which on Minmus generally isn't a problem for anything with rockets, but when it landed, was subject to mysterious forces that drive it in swerving, crabwise circles even with the brakes on.  This force persists even in flight, the pilot cannot perfectly center the prograde or retrograde navball.

There's 0.-0.2 force on three of the wheels, very weird on Minmus.

Am I doomed?  I've got an escape vehicle if I have to, but this had been working so well...

Answered my own question.  I manhandled and RCSed the rover into stopping long enough it'd let me go to the tracking station, and when I returned to it, it was fine again.  Whew.

[Rocket In My Pocket]

I've been hearing a lot about landing gear/wheels jumping on load lately, so that's no mystery anyways.

Personally, I've had vehicles hit the ground or something else so hard it seems to "twist" the parts making it up at their nodes. I'm not aware that this is an intended feature; I don't think it is myself.

I see you have RCS on it, might be worth re-loading and trying for a softer landing if that is indeed what happened?

(Off-topic, I love how you did the screenshot with the zoomed circle, did you do that manually via edits or is it some kind of mod?)

Edited December 9, 2017 by Rocket In My Pocket

[Corona688]

First, the problem is solved, manhandling the rover stationary, quitting to the tracking station, and going back in removed whatever problem there was.

This is Minmus, so the landing was real soft, but whatever clipping launched it 50m into the air probably wasn't!  See that flag by the wheel?  It got clotheslined on load - thought it was a flying part at first.

As for the picture in picture, that's just editing.  I was going to post it in "what did you do today", then changed my mind, then things got weird.

[Plusck]

Yes, I can confirm that this is sometimes an issue for me.

I certainly don't have any idea why it happens. I don't recall anything unusual happening or being done by me before it happens. It is possible that I mashed a few keys at the same time, but then that is something that can happen anyway and KSP doesn't seem to have a problem with multiple concurrent key presses all the rest of the time.

So it's a mystery. And rare, maybe happening three times in my current career save (10 years, all stock planets and moons visited and landed at least once).

If you can get back to the space centre then it is "sorted" when you load the craft again... assuming you have a craft to come back to...

[bewing]

Did you try canceling trim? I'm just wondering if trim might have been causing the problem.

 

[Corona688]

On 12/10/2017 at 2:12 AM, bewing said:

Did you try canceling trim? I'm just wondering if trim might have been causing the problem.

 

Yes, I did.  I also tried turning off all reaction wheels.  Whatever it was, wasn't trim.  Good idea though.

[Corona688]

On 12/9/2017 at 6:04 PM, Plusck said:

I certainly don't have any idea why it happens. I don't recall anything unusual happening or being done by me before it happens.

Some of it comes down to how collision works in computer games, I think.  Objects teleport tick-by-tick, and don't "collide" so much as "overlap".  The game detects that and forcibly shoves them back apart.

Which works great for a pair of spheres, but what about complex shapes?  Moving them apart might just cause them to collide in a slightly different place, and need to be shoved apart again.

Now, which direction is "apart" again?  That's easy to tell if you're a sphere.  Harder to tell if you're a flat square, ragdoll, or donut of fuel tanks.

And what if you have three things in close proximity?  Pushing two apart can shove them into the third.  Then that shoves the first two back together.  You can end up with a balance-point where the forces trying to blow it apart end up keeping their relative positions the same.  Their relative positions.  In game space, the force trying to tear them apart can accelerate them some arbitrary direction.

Depending on how well these corners are handled, you either get KSP or Skate 3.

 

[boccelounge]

Have you confirmed that you're controlling the rover from the correct point?  I assume that HECS core was used for landing...  but the rover should be driven by a forward-facing control point.  I often find that control points are changed when re-loading a vessel with multiple/perpendicular cores.  I always turn on the brakes and turn off SAS when leaving a rover, then reset 'Control From Here' when I return to the vehicle.

Apologies if I'm stating the obvious and/or this is something you've already ruled-out, but that "up-facing" HECS looks mighty suspicious...

[Geschosskopf]

Another general rover guideline....  I find it's a VERY helpful thing to remap the rover controls away from WASD.  Personally, I put them on the numpad.  Thus, WASD for torque and KP8/4/5/6 for driving.

The reason for this is this that the individual parts don't know or care what type of vehicle you're controlling or what you're trying to do with it.  When they see their input keys pressed, they do their thing.  Thus, if you leave the rover controls on WASD, you get both torque and rover steering/acceleration.  This often is a bad thing.  I think it also sometimes contributes to this phantom torque issue.  Wheels are wonky to begin with.

[Corona688]

17 hours ago, boccelounge said:

Have you confirmed that you're controlling the rover from the correct point?

The rover was literally scraping itself around in a circle with brakes on and reaction wheels off (all of them).  No matter how funky your PoV that's not supposed to happen.

4 hours ago, Geschosskopf said:

Another general rover guideline....  I find it's a VERY helpful thing to remap the rover controls away from WASD.  Personally, I put them on the numpad.

I do the exact same

 

[eddiew]

7 hours ago, Geschosskopf said:

Another general rover guideline....  I find it's a VERY helpful thing to remap the rover controls away from WASD.  Personally, I put them on the numpad.  Thus, WASD for torque and KP8/4/5/6 for driving.

This is the best advice for rover drivers, tbh, and I'm annoyed that it's not set like this by default. 

I use cursor keys myself, but the important thing is that I can keep my left hand on torque and my right on the wheel controls, and between them I have very good control over my rovers no matter how crazy their dance moves may get. Jump up, jump back, once you've got the knack you can land it on the wheels every time  

[Geschosskopf]

35 minutes ago, eddiew said:

This is the best advice for rover drivers, tbh, and I'm annoyed that it's not set like this by default. 

Totally agreed.  Also sorry I'm out of likes for today.

[Rocket In My Pocket]

3 hours ago, Geschosskopf said:

Totally agreed.  Also sorry I'm out of likes for today.

I hath liked it for thee good sir!